The recent proliferation of Wi-Fi access points in wireless local area networks (WLANs) has made it possible for navigation systems to use these access points for position determination, especially in areas where there are a large concentration of active Wi-Fi access points (e.g., urban cores, shopping centers, office buildings, and so on). For example, a client device or station (STA) such as a cell phone or tablet computer can use the round trip time (RTT) of signals transmitted to and from the access points (APs) to determine the distances between the STA and the APs. Once the distances between the STA and three APs are determined, the location of the STA may be estimated using trilateration techniques.
More generally, the distance between a first device and a second device may be determined using the RTT of signals exchanged between the first and second devices. A third device may passively listen to the signals exchanged between the first and second devices, and determine distances between itself and each of the first and second devices based on the signals exchanged between the first and second devices. Because ranging operations are becoming more important for determining positions of wireless devices, it is desirable to increase the accuracy of ranging operations.